Some ideas of mine: both things that I already have, or am thinking about buying:

• a nice pedometer/fitbit - measuring your daily activity is the first step towards making sure you do it more regularly, and a good pedometer (with software to see your progress) is within the price range
• a waterpik (to make flossing more interesting and thus more likely)
• a really good-quality umbrella (for areas that are rpone to bad weather) because struggling with flimsy ones is more pain than it's worth to buy a quality one.
• a good quality laptop bag/airline carry-on bag (especially if you lug your heavy laptop around a lot...)
• healthy snacks for while I work (jerky and dried fruit)
• an Ingress addiction (makes me walk a lot and it's free)
• a shoe rack (i have a habit of tossing them all over the floor, and it's an easy way of tidying up the floor while remaining easy to dump my shoes)
• sleep-tracking software and sleep-cycle alarm clock (to wake me up gently during REM cycle - these are often free)
• large prints of nice pictures to stick on the wall behind my computer monitor so I have something nice to look at while working
• do a defensive-driving course (driving safety is always useful for longevity)
• take some meditation classes (for the ability to notice when being distracted and be better able to focus when needed)
• take a toastmasters course (so as to be more confident with public speaking which is an importnat part of being a social leader)
• take up a regularly scheduled low-impact exercise (eg tai chi)